1. Field of the Invention
The present invention relates to a magnetoresistive element that is installed in, for example, a hard disk device or other magnetoresistive device and that utilizes a tunnel effect, and in particular, to a tunneling magnetoresistive element in which a ratio of change in resistance (ΔR/R) can be increased while a small RA (element resistance R×element area A) is realized.
2. Description of the Related Art
Tunneling magnetoresistive (TMR) elements (i.e., tunnel type magnetic sensing elements) are elements whose resistance changes by utilizing a tunnel effect. In such TMR elements, when the magnetization of a pinned magnetic layer and the magnetization of a free magnetic layer are antiparallel, a tunneling current does not easily flow through an insulating barrier layer (tunnel barrier layer) provided between the pinned magnetic layer and the free magnetic layer, and thus, the resistance becomes maximum. In contrast, when the magnetization of the pinned magnetic layer and the magnetization of the free magnetic layer are parallel, the tunneling current flows most easily, and thus, the resistance becomes minimum.
By utilizing this principle, a leakage magnetic field from a recording medium is detected as a change in the voltage based on a change in the electrical resistance, which changes in accordance with a change in the magnetization of the free magnetic layer in response to an external magnetic field. Examples of the related art include Japanese Unexamined Patent Application Publication Nos. 2005-286340 and 2005-260226.
Hitherto, a tunneling magnetoresistive element having a small RA (element resistance R×element area A) and a high ratio of change in resistance (ΔR/R) has not been realized. In general, as the RA decreases, the ratio of change in resistance (ΔR/R) also decreases.
From the standpoint of an effective improvement in the ratio of change in resistance (ΔR/R), in a tunneling magnetoresistive element including an insulating barrier layer made of magnesium oxide (Mg—O), it is believed that the insulating barrier layer, a part of a pinned magnetic layer, and a part of a free magnetic layer, the parts being in contact at the interface with the insulating barrier layer, are preferably formed as a body-centered cubic structure (bcc structure) in which equivalent crystal planes that are typically represented as {100} planes are preferentially oriented on the plane parallel to the layer surfaces.
However, hitherto, in such a tunneling magnetoresistive element including an insulating barrier layer made of Mg—O, a high ratio of change in resistance (ΔR/R) has not been appropriately realized within a range of a small RA.
The inventions disclosed in Japanese Unexamined Patent Application Publication Nos. 2005-286340 and 2005-260226 neither consider the above-described problems nor describe means for solving the problems.